Quiet Your Gun with an AMTAC Suppressor

Keith Wood
-
May 16, 2016

Sound suppressors have grown from a tiny niche market to a large mainstream industry, seemingly overnight. As the industry grows, the technology is improving at a rapid pace. The practical applications of suppressor use are also extending beyond tactical shooting to include the hunting community.

Today's suppressors offer numerous benefits, including reduced noise and light signature, less overpressure from the muzzle blast reaching the shooter and bystanders and reduced felt recoil. Despite these benefits, however, there are some aspects of suppressors that many shooters still consider serious drawbacks.

Suppressors can add significant length to a firearm, compromise balance and cause fairly significant point-of-impact shifts downrange. Utah-based AMTAC is a relatively new player in the suppressor market, but the company set out to specifically address what it saw as shortcomings of other products on the market.

AMTAC makes a full line of precision-machined suppressors in both 5.56mm and 7.62mm versions.

Like firearm manufacturers, suppressor makers come from all sorts of backgrounds. Many companies do very little (if any) of the manufacturing themselves, preferring to subcontract the work out to capable machine shops.

AMTAC came from the other direction: its founders have spent the last three-plus decades as an ISO-9001-certified manufacturer of precision OEM components for the aviation, defense and medical device industries. Its clients, including firms such as Northrup Grumman and ATK, are the kind that demand perfection. As an aerospace-certified shop, AMTAC is accustomed to building quality parts with super-tight tolerances.

AMTAC's owner is a gun enthusiast who originally bought a handful of suppressors for his own use but was disappointed with their performance. He was unhappy with the blowback, the weight, the change in balance and the excessive overall length on the suppressors he purchased.

As a lifelong machinist, he thought that he could build something better than what he'd bought and set out to build his own design — not as a manufacturer, but as an individual using what's called a "Form 1" (an application to make and register an NFA firearm or suppressor). His prototype worked extremely well and after friends and associates continued to ask him to build them one, AMTAC was born.

A Different Design

Most suppressors on the market attach at the muzzle and project forward, adding length and forward weight to the firearm. AMTAC's suppressors are designed to fit over the barrel so that the suppressor actually threads onto the muzzle and extends rearward. Because 6 inches of the suppressor is behind the muzzle, most of AMTAC's suppressors add only 3.7 inches of length to a rifle.

Due to AMTAC's over-barrel design, a compact overall barrel length can be maintained when the suppressor is mounted.

Unlike other over-barrel designs, however, AMTAC's suppressors do not use a special collar to align the suppressor nor is the barrel used as one of the walls of the suppressor. So long as the barrel diameter will clear the inside of the suppressor, it will fit without any other modifications.

Available Models

AMTAC has four suppressor models: the CQB, CQBm, SBR and Sniper, and each model is available in either 5.56mm or 7.62mm versions. Both 5.56mm and 7.62mm versions are the same size, externally.

The flagship of the AMTAC lineup is the CQB, which is designed to fit on a 16-inch AR-15-style barrel with a carbine-length gas system. It threads directly onto the 1/2-28 threads that ordinarily hold the flash hider (or 5/8-24 in the case of a 7.62mm AR), so no special muzzle devices are required. With a CQB suppressor in place, a 16-inch AR's effective barrel length is only 19½ inches. With a diameter of 1.62 inches, the CQB will fit underneath many free floating forend tubes.

The CQBm model is identical to the CQB, but it extends only 4 inches over the barrel. It's designed for a 16-inch barreled AR with a mid-length gas system, and when it's installed on a 10.5" barrel with a pistol-length gas system, practical barrel length is only 14 inches. I don't know of any other detachable suppressor on the market that can make such a claim.

AMTAC's suppressors can be attached to any rifle or carbine with the correct barrel thread and gas block clearance. No special adaptors are required, making the units compatible with a wide variety of firearms.

The SBR is a traditional end-mount suppressor instead of an over-barrel design. This 7.7-inch suppressor uses a longer version of the same single-piece baffle structure found in the AMTAC's other suppressors, and it can be mounted on any rifle with compatible threads.

The Sniper model is designed for heavier-barreled bolt-action and semi-auto rifles. It adds only 3.7 inches of barrel length and is compatible with any barrel under .960 inches in diameter.

Managing Blowback

If you've shot many suppressed semi-automatic rifles, you know that blowback is a significant issue. Blowback occurs when the propellant gases from the cartridge become trapped within the suppressor and travel backward into the shooter's face when the action is cycled.

With many suppressors, the shooter gets a face full of hot gas with every pull of the trigger. The problem is compounded for left-handed shooters due to the position of their face relative to the ejection port. One of AMTAC's goals was to reduce blowback, especially since its lead designer is left-handed.

Unlike many other suppressors, each of AMTAC's over-barrel models feature a 4-inch or 6-inch internal baffle chamber, which is housed in the rearmost portion of the suppressor. That large volume chamber allows propellant gases to expand and dissipate, which significantly reduces blowback and also reduces the amount of carbon fouling that is pushed back into the working parts of the firearm.

This technology allows the gun to run cleaner and reduces the risk of malfunctions related to excess carbon buildup. Several police departments have transitioned to AMTAC suppressors for their SWAT teams for this reliability enhancement.

The large blast chamber offers another advantage that AMTAC's designers took advantage of: a patent-pending design that ports gasses back into the first baffle, which cuts recoil forces by acting as an internal muzzle brake.

A Quieter Report

As far as sound suppression goes, all AMTAC's suppressors are hearing safe. The perceived loudness of a suppressed rifle is a tough subject to address in print. Test equipment that measures in decibels (dB) is the industry standard method of measuring the sound reduction of suppressors, but it doesn't always tell the entire story. Many shooters have commented that AMTAC's suppressors sound quieter than other models that have better dB ratings.

AMTAC's thread mount and baffles are machined from a single piece of stainless steel to ensure perfect alignment.

Whether this is a function of how the human ear processes sound or a weakness in the current measuring equipment isn't clear. Ironically, AMTAC's parent company builds components for the decibel-measuring equipment used by most of the suppressor industry.

Reducing POI Shifts

Point-of-impact, or POI, shift is another drawback of attaching a suppressor to a firearm. POI shift can run from slight to significant and seems to vary with each design. POI shift is often caused by turbulence in the bullet's flight caused by the propellant gases passing over baffles that are imperceptibly uneven.

AMTAC's thread mount and the concentric relationship between the mount and the bore ensure POI and zero shift are held to an absolute minimum.

Because of AMTAC's experience machining products for the aerospace industry, the company is able to hold extremely tight tolerances during the manufacture of its suppressors. The 17-4 PH stainless steel thread mount and baffle stack on all AMTAC products is a single homogeneous unit that is machined in a sequential series of operations on CNC equipment without being removed. This results in minimal variability between the single-point cut threads and the suppressor bore.

Another factor in POI shift is often the variability allowed by non-threaded, fast-attach mounts. Though slower to attach and remove than other designs, a threaded mount will always be more secure and repeatable, that said, the over-barrel nature of these suppressors also makes them faster to attach than many other thread-mount units.

Because of the thread mount and the concentric relationship between the mount and the bore, POI and zero shift are held to an absolute minimum with AMTAC's suppressors. AMTAC has never seen or heard of a baffle strike (a projectile hitting an internal baffle) on any of its products, which is a great testament to that alignment.

A patent-pending design on AMTAC suppressors ports gasses back into the first baffle, which cuts recoil forces by acting as an internal muzzle brake.

Choosing a suppressor can be a bit overwhelming, especially since the legalities of NFA transfers make it difficult to try a product before you buy it. AMTAC started by dipping its toe into the industry in early 2015 and now is growing its footprint in full force.

AMTAC's line offers excellent options for shooters looking to maximize the performance of a suppressor while minimizing the side effects of increased length, poor balance, gas blowback and POI shift. These suppressors attach directly to America's most popular rifles without additional tools or mounts and do so without adding unnecessary bulk. All AMTAC products come with a lifetime warranty.

AMTAC is releasing a free ebook for prospective suppressor owners and is has also announced a giveaway for a free suppressor, complete with $200 to cover the cost of the tax stamp. Check out their website for details.

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